Newegg is currently offering 100 4.7GB DVDs at a taxfree price of $23 with free shipping. At a fill-rate of 90%, or 4.2GB per disc, this option comes out to 18.26 GB. per dollar.
Newegg is also offering an external hard drive, a Fantom Drives G-Force G1000EU 1TB for $95, $75 with rebate. This option comes out to 10.53 GB per dollar.
The DVDs are still a better choice of storage media for now.